'75 Yamaha XS500 Cafe Project - Open Throttle

[SrgtBear]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Sooo Close - 10/17

It's been awhile since I made any updates. I took a few weekends off and took a trip down to Austin, TX to visit a friend then a trip to DC the weekend after for a party.

Anyways, the bike is so close to being done I can taste it. Not much left. Mounted rear tail light which looks bitchen and finally got the hardware for the center stand. The center stand is a bitch to put down but it looks cooler and sits safer.....thats if you don't drop your bike trying to put it down. If someone has a better technique let me know. Right now it involved standing on the center stand and pulling the rear up by the frame. I only weight 150lb. Pics below.

To do list:
Rebuild Petcocks
Rear Turn Signals
Front Fender
Upholster Seat
Bondo Tank to clean up knee inserts
Prep & Paint

 

[SrgtBear]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Long Awaited Update - 4/3

Current status. It's been test driven. It sounds mean. It feels mean. It just needs a seat cushion, paint, and carb sync. All done very soon.
Things you may notice include bondo tank work. Formed knee inserts after I hammer them in a little. New taillight. Turn signal below the seat. All blinking correctly after I added some resistors. Also cut front fender. My only regret is that I didn't take video of the test drives. Other than that timing has been adjusted and just needs a carb sync.

Before Bondo Work, rear turn signals and front fender:

 

[saywhat]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Long Awaited Update - 4/3

Glad to see you back in action!

 

[two-smoker]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Long Awaited Update - 4/3

Looking good!

 

[Swagger]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Long Awaited Update - 4/3

That's coming together really nicely, one of my favorite 'unsung' motors too!

 

[JRK5892]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Long Awaited Update - 4/3

the motor looks awesome! what jets you runing on those carbs with pods?

 

[SrgtBear]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Long Awaited Update - 4/3

the motor looks awesome! what jets you runing on those carbs with pods?

#135

It fires up and runs with no problem. However I just noticed I am having low idle problems. Firing of 1 and 1/2 a cylinder. (Right Cylinder weak at idle and slow turns.) I know it's timed correctly because mid and top end runs at tip top shape. Gotta go back and check the float bowl height and sync carbs.

As far as the jet, I haven't been able to tell if it's running to rich, but I am having great mid-range and top-range. No smoke. I'll check the plugs later.

 

[JRK5892]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Long Awaited Update - 4/3

same thing i was running into... problem is onece the carbs where synced the motor would race at idol after i came off the throttle while riding. so i would lwoer the idol then it would die... i got sick and tired of fussing with it... hope you have better luck. I changed carbs. keep me updated bud bike looks great!

 

[saywhat]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Long Awaited Update - 4/3

I hope you guys figure out the carb issues before I get mine up and running, I'm not looking forward to the impossible tuning with pods and open exhaust

 

[SrgtBear]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Long Awaited Update - 4/3

I hope you guys figure out the carb issues before I get mine up and running, I'm not looking forward to the impossible tuning with pods and open exhaust

I am going to be honest. I don't think the open exhaust setup works on this bike. I think back pressure is the key to this bike. I read alot of stuff on the internet and kept hearing the same things. I don't have quite the same symptoms as Joe. My idle doesn't shift up and down. My one cylinder is just weak or not firing at idle and low rpms. According to the service manual the float bowl may not be sitting right. (which makes perfect sense for my problem.) Still I would try to figure something out for an exhaust.

These reverse cones on mine are super nice. They still sound real great and loud with the baffle. They will come with couplers to get them to fit right. I had to cut about 1 inch and 1/2 off the end of the headers to get them to go strait.

 

[JRK5892]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Long Awaited Update - 4/3

i ahve full baffles in my pipes as well i could not even come close to get the bike run with open pipes, plus it sounded like crap

 

[Swagger]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Long Awaited Update - 4/3

SrgtBear has hit it on the head.
Lots of guys will swear up and down that you can run CV carbs open, with Velocity stacks or pods. While it *can* be done, the simple fact is it takes a LOT of tuning and several key mods. You can drill out the transfer port(s) in the slide and take care of some of it but not all. I saw a bike with an external vacuum reference added to each carb but talk about beating a dead horse! You could make chambers that slip onto the mouths of the carbs from ABS plumbing pipe, say...8" long with a partially blocked opening and slip long foam filters over the whole length to hide the tube. That might help but again.....pounding away at the deceased equine.

The problem is that without the OE back-pressure at the mouth of the carb that is given by the stock airbox, and some additional back pressure from the exhaust....the slides in those CV carbs simply won't meter the fuel correctly. The results are often boggy throttle response (already one problem with CVs), hanging idle, erratic idle, burned pistons, stinky feet and bad breath.

The simplest plan to get this running smoothly would be to sling the stock airbox back on and re-jet to suit your more open pipes. That would certainly be adequate if not entirely bitchin.

Or......
go to your parts retailer of choice and pick up a pair of VM30's and jet them as needed to run your pipes and open element intake. Not only will you have manual control of the metering via the throttle cable itself but you will have a far broader range of tuning.

 

[two-smoker]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Long Awaited Update - 4/3

I never even tried to run stock carbs on mine... The mikunis showed up last Thursday, along with my new tank off a 78. So that's what I'm running. I've heard bad things from too many people. What gets me is, I had no trouble running keihin cv's with pods and an open exhaust on my cb450....

 

[Big R]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Long Awaited Update - 4/3

Looks great Srg- I still love that chrome on the motor.

 

[saywhat]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Long Awaited Update - 4/3

Do you guys have the BS38 Mikunis, or the earlier Keilins (sp?), I guess they changed to Mikunis in '76 and they are supposed to be a little more tune/bolt-on friendly.

 

[Rossicle]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Long Awaited Update - 4/3

I'm blown away by that engine! It's beautiful! Can't wait to see the rest of the bike finished.

 

[two-smoker]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Long Awaited Update - 4/3

Do you guys have the BS38 Mikunis, or the earlier Keilins (sp?), I guess they changed to Mikunis in '76 and they are supposed to be a little more tune/bolt-on friendly.

I had the earlier Keihins. Now I have Mikunis. (sorry to thread jack)

 

[SrgtBear]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Baby's got some fine lines 4/17

Got some new pics. Trying to stay more active on here as much as I can. Also trying to keep busy on my bike with the peak of the summer right around the corner. My upholstery guy was away this weekend so I'll have to wait till next weekend to drop off the seat. The good news is that I was able to work on a couple odds and ends.

Below you'll see the front fender and side covers. I scuffed up the front fender real good and put a layer of bondo on it so I could paint on it later. It's a little short so at this point it's mostly about looks.

I kept cutting the side covers down until I got the lines I wanted. I'll fill in the dents and stuff before I paint.

Finally, a complete picture with fender and side cover. I got the admit that the bike has some great lines. Came together real nice.

P.S. I am missing a rubber grommet for the upper right corner of my left side cover. If anyone has an extra one I could definitely use it.

 

[SrgtBear]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Paint: Your Vote is Needed. 5/1

I've been throwing around paint schemes for the last year and now I finally ready to lay it down. I think at this point I could use some peoples opinions on which way I should go. REDnBlack or BlacknRed? Personally I love them both. Below are the samples I'll be working with, followed by my poopy photoshop mach-ups. Let me know what you think.

REDnBLACK:

BLACKnRED:

 

[valvesprung]

Re: 1975 Yamaha XS500B Cafe Project (TX500) - Paint: Your Vote is Needed. 5/1

Red usually isn't my thing, but I say REDnBLACK all the way man. Looks crazy classy...